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Plant Issues (Please take a moment to look)

Thread starter #1
this particular plant has been grown under a 4' X 2' T-5 fixture (200w)
20/4 light cycle. it has been grown from seed and has been vegging for about 6weeks. it is a little on the small side as are the others that were started.
I have used no fertilizers and have only used filtered water. my watering regime is to water them when the leaves start to droop slightly. seems to work out fine, personally i see no signs of over watering. but i noticed a brown splotch almost resembling rust on one of the leaves, it was also curling into itself. The medium in which i`m growing it is just soil, but good soil all the same.
although i have not yet set it into flowering i have a strong suspicion it's male.

please if anyone knows what this is and how to deal with it PLEASE let me know, although I'm new to growing i suspect this may be a disease or fungal growth starting. i by no means want this to spread to my other healthy plants.

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You have not said what your growing in so the only thing we can tell you from your info is that 6 weeks is far to long to go without nutes. Even if you are in enriched soil. If your worried about desease which I doubt cut off the infected part and throw it out.
That looks just like what I am seeing on a few of my plants. They are around the same age and in soil. Except I am using Foxfarm Grow Big. I also have the couple of rust spots like you are seeing. I think it had something to do with heat. I have a quantum badboy t5 4' with 4 bulbs in my closet. I also was doing 24hr light with the closet door closed. In any case, I thought it was getting too hot in there so I dropped the lights schedule to 18/6. I also turned the ac on in the room and left the closet door cracked open for ventilation. And that seems to have stopped the curling issue.

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Thread starter #6
just a little update, the ''rust spot'' has progressed outward, and i am now seeing it slowly emerge on my other plants. i am very worried about this, i can only hope it's just a nutrient deficiency. I'll post some pics tomorrow and i'll pick up some ferts with micro nutes. This guy, i must agree with you that heat may be an issue but this seems to be something different than what you're dealing with. you'll see when i post pics. on another note, VERY nice looking plants, definitely better than mine, i've been neglectful...
It could be a phosphorous deficiency, but it might not be for lack of phosphorous, may be locked out because of pH issues.
Thread starter #8
yes i've considered that it may be a ph issue, i haven't tested either soil or water.
i must go and get myself a ph tester. here are some new photos, i apologize for the quality, the bright lights must screw with the camera to a degree. i am leaning towards nutrient deficiency now, due to the new leaves being VERY light green, or nutrient lockout as freaknature mentioned due to unbalanced ph levels. i added some miracle grow the other day (only because i had nothing better on hand) and as far as i can see the ''rust spots'' have stopped in their tracks. but any other opinions on this matter are still much appreciated as i am not 100% sure either way.

I am going to go with freaknature it looks like a phosphorus deficiency deficiencys are some what common and are often misdiagnosed.Deficiencysare most common when the growing medium ph is over 7and phosporus is unable to be absorbed properly or the soil is acidic below 5.8 ph or last but not least if there is a excess of iron and zinc and the soil has become fixated (chemicaly bound) with phosphates.hope it helps
Thread starter #11
just got a reading of 6.0 ph, with a ph meter. that is prime from what i understand.
so i guess they were lacking nutes, i have fed them 20-20-20 with micro nutrients, and now they seem to be doing fine. at least there has been no progression of the ''rust spots'', and the excessively light green new foliage is looking better as well.
they will be transplanted outside soon enough, and then everything will, for the most part take care of itself. thanks for everyone's input on this matter, i do appreciate it, but if you happen to have a definitive answer as to what nutrient the plants were lacking I'd still like to know.
6.0 in soil is not prime, more like extreme low end. 6.5-6.8 is usually considered best for Cannabis in soil. There's a 10x difference in pH between 6.0 and 7.0.
you may want to use some hydrated lime.
i use bonide in my mix.:thumb:
use 1 tea. per gallon to sweeten the soil and raise the ph a bit.
or you could dress it on the top of the soil.
just don't let it touch the leaves.
i recommend the 1 teaspoon per gallon. this will bring your ph up slowly.